Reasons? [Study As­sess­ment]

posted by Helmut Homepage – Vienna, Austria, 2021-08-21 21:43 (64 d 12:42 ago) – Posting: # 22531
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Hi Dshah,

I can’t follow your arguments.

» 1. Same subjects? With subject changes- concentration also changes a bit.

Agree. However, each study stands on its own since the T vs R comparison is done within subjects. Imagine: One study is performed in ballerinas and the other in Sumo wrestlers. Likely different volume of distributions and hence, concentrations in the first study will by higher than in the second. Nevertheless, the T/R-ratios will be similar.

» 2. Same BA method?

Even if different ones are used (unlikely cause Mehul mentioned the same CRO) and if both methods are validated, different Cmax and similar AUC are unlikely as well.

» 3. Same Internal standard batch? Change in internal standard changes height and thus ultimately concentration.

Given, the IS response might be different. However, even if calibrators and QC samples are prepared with, say, an IS of just 50% of the declared content in one of the studies, the back-calculated concentrations should be similar and therefore, the T/R-ratios.

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